No matter how old you are or where you live, there's a good chance that you could be deficient in vitamin D. A study published in the New England Journal of Medicine reported that an estimated 1 billion people worldwide have inadequate amounts of vitamin D in their blood.

You probably know that vitamin D plays a role in keep your bones healthy, but did you know that getting enough vitamin D (along with calcium) is associated with maintaining a healthy weight as well? In fact, a study found that calcium and vitamin D may lead to a beneficial reduction in belly fat in overweight adults.

Plus, being deficient in vitamin D may increase your risk for diseases such as osteoporosis, heart disease, even some cancers and the flu. So how much vitamin D do you need to eat each day? The National Health Institute now recommends that people between the ages of one and 70 consume 600 international units (IUs) of vitamin D each day with an upper limit of 4,000 IUs per day. However, many doctors and dietitians believe people need even more than 600 IUs a day for optimal health.

To get plenty of vitamin D in your diet, it takes a little planning since very few foods naturally contain vitamin D. Fortified products like dairy foods and breakfast cereals can help you meet your vitamin D needs. Here are some foods with the highest content of vitamin D:

3 ounces of cooked Sockeye Salmon contains 447 IUs

84 grams (about 1/3 cup of mushrooms) provide between 3 (naturally occurring) and 493 IUs (mushrooms grown with exposure to UV light) depending on variety and how they are prepared